Cooling arrangement for magnetron

ABSTRACT

A magnetron device composed by improving the medium or large size magnetron device having an output power of the order of 500 watts in ultrahigh frequency, which comprises as cooling means an assembly of a natural air-cooled type radiator formed of aluminum or alloy thereof and which, accordingly, does not necessitate the cooling means like blowers provided to conventional devices. Said device has such advantages that noise is eliminated during operation and that it is light and compact and therefore it is particularly suitable for a domestic-use microwave range.

United States Patent Inventors Yoshio Kato Minoo'shi; Yasuo Ishida,Hirakata-shi, Japan Appl. No. 757,901 Filed Sept. 6, 1968 Patented Apr.20, 1971 Assignee Matsushita Electronics Corporation Osaka, JapanPriority Sept. 7, 1967 Japan 42/57759 COOLING ARRANGEMENT FOR MAGNETRON5 Claims, 4 Drawing Figs.

US. (I 315/32, 165/185, 219/1055, 313/45, 315/3951, 317/100 Int. Cll-10lj 7/26, HOSb 9/06 FieldofSearch .L 313/11,.30,

[56] References Cited UNITED STATES PATENTS 3,304,400 2/1967 Ojelid 3 l3/45X 3,323,020 5/1967 Lenart et al. 219/l0.55X

. FOREIGN PATENTS 855,272 1 1/ 1960 Great Britain 313/45 PrimaryExaminer-Robert Segal Assistant Examiner-E. R. LaRoche Att0rneyStevens,Davis, Miller and Mosher ABSTRACT: A magnetron device composed byimproving the medium or large size magnetron device having an outputpower of the order of 500 watts in ultrahigh frequency, which comprisesas cooling means an assembly of a natural aircooled type radiator formedof aluminum or alloy thereof and which, accordingly, does notnecessitate the cooling means like blowers provided to conventionaldevices. Said device has such advantages that noise is eliminated duringoperation and that it is light and compact and therefore it isparticularly suitable for a domestic-use microwave range.

PATENIEDA-PRZOWI 3,575,632

' SHEET 1 0F 2 INVENTORS yMH/D lf/QT yes 0 IsH/DH ATTORNEYS COOLINGARRANGEMENT FOR MAGNETRON This invention relates to the improvement of anatural aircooled type magnetron device.

In a continuous-wave magnetron device composed by installing a medium orlarge size magnetron tube body having an output power of about 500 wattsin ultrahigh frequency, a forced air-cooling system has been employed asmeans to cool the magnetron tube. Namely, the exterior part of the tubeincluding the anode of the magnetron is disposed in the air duct and ablower is provided at one end of the air duct to dissipate the anodeheat generated by the anode loss of the magnetron device.

According to such forced air-cooling method, however, not only themechanism of the cooling system becomes large and complicated, but alsoindirect costs are expensive to operate the blower and the noise of theblower is offensive to the ear.

A so-called natural air-cooled type device, which does not comprise saidblower as cooling means for the conventional magnetron device, butcomprises radiator fins provided directly to the anode of. themagnetron, is also used in a small output magnetron device. According tosaid structure, however, it is only possible to cool magnetron devicesof output power of about 200 watts in ultrahigh frequency.

This invention is intended to obviate the above deficiencies present inthe conventional magnetron device and an object of this invention is toprovide a magnetron device comprising natural air-cooled type radiationmeans which can cool a medium or a large size magnetron device of anoutput power of the order of 500 watts in ultrahigh frequency.

Another object of this invention is to provide a natural aircooled typemagnetron device having a good radiation ability.

A further object of this invention is to provide a natural aircooledtype magnetron device with a compact packaged radiator and a magneticfield generator simple to assemble and useful for a domestic-usemicrowave range.

The magnetron device according to this invention comprises a body of anelectron tube capable of microwave generation, a magnetic fieldgenerator coupled magnetically thereto and a natural air-cooled typeradiator directly connected to the anode of said electron tube body and.it is characterized in that said radiator is composed by assembling adisc core and a large number of radiator fins wherein said core part isclosely adhered to said body of the electron tube at the center andfixed to said radiator fins at the end of said core part. Said radiatorhas the heat conduction characteristics to radiator fins that thetemperature difference between the central hole part and the end part ofthe disc core is kept less than 50 C. during operation. Said :radiatoris formed of a light metal having good thermal conductivity likealuminum or alloy thereof. In this magnetron device, the disc corecomposing a part of said radiator has a main surface, the form of whichis rectangular or modified-rectangular, perpendicular to the axis ofsaid magnetron tube, said magnetic field generator is provided on saidmain surface and in the side space outside the end part perpendicular tothe short side of said main surface and radiator fins composing theprincipal component of the radiator of said device are fixed on both endparts perpendicular to the long side of said main surface and disposedat the circumference surrounding said magnetron tube body and saidmagnetic field generator.

In the magnetron device of this invention, the disc core of the radiatorhas a practical dimension such that the-weight thereof is aboutpercent-60 percent of the total weight of the radiator.

Other objects, features and advantages of this invention will be readilyapparent from the following detailed description of certain preferredembodiments taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a fragmentary sectional diagram of a natural aircooled typemagnetron device embodying this invention;

FIG. 2 is a plan view of a natural air-cooled type magnetron deviceembodying this invention;

FIG. 3 is a plan view of a radiator structure of a magnetron device ofthis invention; and

FIG. 4 shows the thermal characteristics of a magnetron device of thisinvention during a typical intermittent operation and shows thevariation of the anode temperature with time.

In FIGS. 1 and 2, reference numeral 1 designates a medium sizemagnetronof an output power of about 500 watts in ultrahigh frequency and 2designates the anode block which is the outer part of the anode made ofoxygen-free copper and extends in a ring form out of the tube. Referencenumeral 3 indicates the disc core made of light metals having goodthermal conductivity like aluminum or alloy thereof. It has a thicknesssubstantially equal to the height of the anode block 2 and adheresclosely to the anode block 2 of the magnetron l penetrating through thecenter hole 4 by soldering or adhesion with a thermal conductive resin.The excitation coil or the permanent magnet 5 and the yoke 6magnetically coupled thereto compose the magnetic field generator 7 forthe magnetron I. The large number of fins 8, formed of light metalhaving good thermal conductivity like aluminum or alloy thereof,comprise base parts 8 fixed by a screw clamp to the outer end part ofthe core 3 which together with said fins 8 compose the radiator, and themain parts 8" extending along the axis of the magnetron tube I anddisposed higher than said magnetic field generator 7 in the outer spaceof said generator 7. The main parts 8" of the two fins placed at the twoends of the core are arranged so that the surfaces may face each otherat a certain distance as shown in the figure. The main surface of thecore 3 has a width sufficient to incorporate said magnetic fieldgenerator 7 placed thereon. It has proved preferable that thetemperature difference between the circumferential part of the centerhole 4 of the core 3 and the outer end part of the core 3 is smallerthan about 50 C. in view of the relation between the outer ambienttemperature in usage and the maximum allowed temperature of the anode ofthe magnetron l.

The weight of the core 3 is about 20 percent-60 percent of the totalweight of the cooling means. When an example of a concrete size of thecore 3 is given with reference to FIG. 3, m is 133 mm., m is mm., thethickness is 37 mm., the minimum cross-sectional area along the YY'cross section is 27 cm., the maximum area is 48 cm, and the weight ofthe core made of aluminum is about 1.5 kg. The total weight of the twogroups of fins made of aluminum whose total surface area is 0.82 m. is3.2 kg. The size of m. relates to the size of magnetic field generator7, but must be made larger than about 30 mm.

The device comprising the cooling means having said values exhibits thecharacteristics shown by the solid line a in FIG. 4. The same figureshows the variation of the anode temperature when the repetition of l5minutes operation and 15 minutes rest is made at a room temperature of25 C. It is understood that this device has a colling ability superiorto the one of the forced air-cooling shown by the broken line b. It isalso understood that the temperature rises gradually so that the devicedemonstrates an excellent radiative effect when it is applied to adomestic-use microwave range used in such transient characteristicregions.

As has been described hereinabove, the natural air-cooled type coolingmeans of the device according to this invention are composed of a largenumber of fins arranged in the outer space of the magnetic fieldgenerator and the core for thermally connecting the substrate of thefins to the anode block of the magnetron tube. The size and the heatcapacity of said core are made sufficiently large to mount the magneticfield generator thereon. Further, the difference between the temperaturearound the center hole of the core and the temperature at the outer endpart of the core is made less than about 50 C., so that when the anodetemperature of the magnetron rises during the operation of the device,the temperature of the outer end part of the core or the substrate ofthe, fins also rises and the heat generated is effectively dissipatedinto the outer space by the group of fins by natural convection mainly.Further, a large number of fins can be provided to the core and thecooling device substantially covers and mechanically protects themagnetron tube. Thus mounted, and a pair of groups the device of thisinvention is particularly effective when used for a domestic-usemicrowave range having an output power of the order of 500 watts inultrahigh frequency.

We claim:

1. in an air-cooled magnetron device comprising a magnetron tube and amagnetic field generator magnetically coupled to said magnetron tube, acooling arrangement comprising a substantially rectangular board havinga hole at the center thereof to which the anode block of the magnetrontube is fitted and on which the magnetic field generator is of finsattached to the opposite side-faces of said board, said groups of finsbeing disposed so as to protect said magnetic field generator.

2. A cooling arrangement as defined in claim 1, wherein said fins aredisposed in such a manner that the surfaces of i5 said fins are parallelwith the main axis of the magnetron tube and with the opposing directionof said pair of groups of fins.

3. A cooling arrangement as defined in claim 1, wherein the weight ofsaid board is 20 percent to 60 percent of the total weight of saidcooling arrangement, and the difference between the temperature of theperipheral part of said hole in said board and the temperature of theedge part of said board where said group of fins are attached is lessthan C. during the operation of said magnetron tube.

4. A cooling arrangement as defined in claim said board and said finsare made of aluminum.

5. A cooling arrangement as defined in claim 1, wherein said board andsaid fins are made of an alloy of aluminum.

1, wherein

1. In an air-cooled magnetron device comprising a magnetron tube and amagnetic field generator magnetically coupled to said magnetron tube, acooling arrangement comprising a substantially rectangular board havinga hole at the center thereof to which the anode block of the magnetrontube is fitted and on which the magnetic field generator is mounted, anda pair of groups of fins attached to the opposite side-faces of saidboard, said groups of fins being disposed so as to protect said magneticfield generator.
 2. A cooling arrangement as defined in claim 1, whereinsaid fins are disposed in such a manner that the surfaces of said finsare parallel with the main axis of the magnetron tube and with theopposing direction of said pair of groups of fins.
 3. A coolingarrangement as defined in claim 1, wherein the weight of said board is20 percent to 60 percent of the total weight of said coolingarrangement, and the difference between the temperature of theperipheral part of said hole in said board and the temperature of theedge part of said board where said group of fins are attached is lessthan 50* C. during the operation of said magnetron tube.
 4. A coolingarrangement as defined in claim 1, wherein said board and said fins aremade of aluminum.
 5. A cooling arrangement as defined in claim 1,wherein said board and said fins are made of an alloy of aluminum.